What hunter-gatherers can tell us about human social networks

Hunter-gatherers have a three-tiered social
network to increase the chance the whole community has enough to eat, according
to new UCL research which looked at two contemporary hunter-gatherer groups.

Published today
in Current Biology, the researchers studied
the Agta, of northern Luzon in the Philippines, and the Mbendjele who live in
the north of the Republic of Congo.

For the Agta, the
primary source of protein is fish, supplemented by inter-tidal foraging,
hunting, honey collecting, and gathering wild foods. The Mbendjele source most
of their meat from forest-hunting and subsidise their protein intake by collecting
honey, gathering wild foods and occasionally fishing.

"At times,
foragers may procure more than enough food to feed themselves while at others
they may go days or weeks without producing anything," said first author Mark
Dyble (UCL Anthropology). "Because of this, the sharing of food is vital for
the survival of hunter-gatherer communities. It is likely this is as true for
hunter-gatherers in the past as it is for hunter-gatherer communities today."

Last author Dr Andrea
Migliano, (UCL Anthropology) and PI of the Hunter-Gatherers Resilience Project
funded by the Leverhulme Trust, explains how a multi-level social structure
exists within hunter-gatherer communities to structure social life and
co-operation in important activities such as foraging and food sharing:

"Food sharing
and cooperation are central for hunter-gatherers. Hunter-gatherers multi-level
social structure exists in different groups, to help regulate these cooperative
systems. Furthermore, multi-level social structures regulate social rules,
friendship and kinship ties and the spread of social norms, promoting a more
efficient sharing and cooperation. Sharing is a crucial adaptation to
hunter-gatherers' lifestyles, central to their resilience - and central to the
evolution of mankind."

While previous studies
have identified similarities in social structure across different
hunter-gatherer populations, the new work is the first to explore how these
multi-level social networks structure the way individuals food-share.

The team
collected data by living with the two communities for many months, making
observations on how often households shared food with each other. From analysing
this, the researchers could precisely map out the social networks that exist
within the groups.

"Although we had
an idea of how camps split into food sharing clusters 'on the ground,' we were
able to test these using algorithms which are able to identify sub-communities
within the nine camps we studied," Dyble explained.

Their analysis
showed that, in both communities, individuals maintain a three-tiered social
network when it comes to sharing food. The first tier is their immediate household,
most often consisting of five or six individuals; the second social network is
a cluster of three to four closely related households with whom the individual
shares food frequently; the third is the wider camp.

"Despite being
from different continents and living in very different ecologies, both groups
of hunter-gatherers had a strikingly similar social organization," Dyble said.

The similar
results across both groups reinforce the idea that social networks that
structure food-sharing between individuals are essential for all hunter-gatherer
populations to survive:

"Cooperation and
especially food sharing are essential for survival in a hunting-and-gathering
economy," Dyble said. "The proverb that 'it takes a village to raise a child'
is certainly true for hunter-gatherers who, without food sharing to mitigate
the day-to-day shortfalls in foraging, could simply not survive."

Dyble says the
team from UCL now intend to explore the structure of other types of social
networks among hunter-gatherer communities, such as cooperation in childcare,
and compare these with the structures of food-sharing.